Seatroopers of the Galactic Empire used the SG-4 blaster rifle for underwater combat.
The Merr-Sonn Munitions SG-4 blaster carbine was generally promoted as a security and police tactical response weapon. It served as a light duty weapon on some mobile planetary defense units also. Shortly before the formation of the actual Rebel Alliance, agents who would go on to become members of the Alliance posed as law enforcement officials and successfully purchased over 200,000 of these carbines. Some of these weapons were later used by Rebels, with others being scattered over several secret caches. One such cache, containing over 2,000 of these weapons, was discovered by Imperial Security Bureau agents shortly before the outbreak of anti-Imperial hostilities. Presumably, these weapons were either confiscated by the ISB or sold under the table on the black market for an extra profit.
- "Blaster Weapons of the Rebel Alliance" — Challenge 40
- Rebellion Era Campaign Guide